Constant voltage source with output current limitation

Abstract

A constant voltage source is disclosed having an output current control element, which adjusts an output voltage of the constant voltage source by varying its output current, a control circuit, which acquires a measure for an actual value of the output voltage and processes it to a control signal for the control of the output current control element, and a limiting circuit, which limits the output current to a predefined maximum value by action on the control signal, whereby the limitation is independent of an actual value of the output current. Wherein the limiting circuit has a first pair comprising a first transistor and a second transistor and a second pair comprising a third transistor and a fourth transistor, whereby the first and fourth transistor belong to a first conductivity type, the second and third transistor belong to a second conductivity type, operating current paths of the first pair lie in series between a reference current source and a supply potential, the operating current paths of the second pair are integrated in series into the control branch, control terminals of transistors of the same type are connected to one another, control terminals of transistors of the first conductivity type are connected to the reference current source, and control terminals of transistors of the second conductivity type to a first voltage source. Further, a method for generating a load-independent constant output voltage is disclosed.

Description

[0001]This nonprovisional application claims priority under 35 U.S.C. § 119(a) on German Patent Application No. DE 102005061377, which was filed in Germany on Dec. 13, 2005, and which is herein incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a constant voltage source with an output current control element, which adjusts an output voltage (u_out) of the constant voltage source by varying its output current, with a control circuit, which determines an actual value of the output voltage and processes it to a control signal for controlling the output current control element, and with a limiting circuit, which limits the output current to a predefined maximum value by action on the control signal. Furthermore, the invention relates to a method for generating a load-independent constant output voltage with such a constant voltage source.[0004]2. Description of the Background Art[0005]A constant voltage source is kn...

AI Technical Summary

Benefits of technology

[0014]In addition, the series connection of the transistors of the first pair and the transistors of the second pair advantageously make it possible to use higher input or supply voltages.

[0016]In the prior-art circuit, the output signal of a differential amplifier is used directly for controlling an output current-power transistor, as a result of which undesirable reactions by the power transistor to the control signal are possible. These undesirable reactions are avoided or at least reduced by the use of the current mirror, which has a high output resistance.

[0024]The second and the third transistors can be made as high-blocking transistors. As a result, higher input or supply voltages can be used advantageously.

Problems solved by technology

The second feedback no longer applies at all due to the control signal limitation which is independent of the actual value of the output current.

It turned out that the oscillation tendency of the array declines considerably as a result.

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